475 
may contain, and, secondly, upon a knowledge of the most advan- 
tageous methods of extracting their contents. 
Cases are often exhibited in these models of deceptive indications 
of coal upon the surface, when, in consequence of complex faults, 
small portions only of the broken strata remain below; whilst in 
other cases, many and valuable beds of coal may exist below, where 
few or no traces of it appear upon the surface. 
Mr. Sopwith has founded these models on observations made 
during extensive practice, as a mineral surveyor, at Newcastle and 
Alston Moor. The principle of their construction is available to 
represent all kinds of geological phzenomena, and has been applied 
by him, on a large scale, in a model of the entire coal-field of the 
Forest’ of Dean, in which the exact extent and thickness of each 
bed of coal becomes instantaneously apparent on the removal of the 
upper laminz of the model ; each component stratum of the coal- 
field: being represented in its proper place by a moveable lamina 
or stratum of wood, on which a register may be kept of the quanti- 
ties of coal that are from time to time extracted from the collieries. 
The model also at once indicates the most advantageous mode of 
working every portion of the coal-field. 
It is of no small importance to the future welfare of the nation, 
so dependent as we are become for our commercial prosperity 
upon a continued supply of mineral fuel, that similar models 
to that of the Forest of Dean, which has been made by Mr. Sop- 
with for the Office of the Commissioners of Woods and Forests, 
should be also made of other coal-fields, and preserved in the Mining 
Record Office, attached to that department, as permanent registers 
of the amount of coal which is year by year extracted from each of 
these subterranean main-springs of our commercial activity. By 
reference to such models, an estimate may, at any time, be formed 
of the quantity of coal that remains for future consumption ; the 
amount of which will be the measure of the possible duration of our 
country’s exalted position among the kingdoms of the earth. | 
The idea of expressing, by coloured sections, the alternations and 
accidents of stfata, had occurred many years ago to Mr. Farey, 
who, in his “ History of Derbyshire” (1815), has engraved two large 
plates (Pl. III. and Pl. IV.), expressing, in coloured diagrams, many 
similar complex phenomena of faults and fractures, and also the va- 
ried effects of denudation, in cases where the edges of strata, in the 
sides of valleys, vary in superficial extent according to the angle at 
which thesé strata may be inclined. 
MINERAL CONCHOLOGY. 
Your last year’s grant of the proceeds of the Wollaston Fund to 
Mr. Sowerby, has produced the publication of two new numbers of 
his Mineral Conchology, and a third number is on the point of 
being published *. 
* During the last year, Mr. Lyell has called the attention of geologists 
to the importance of a discovery made in 1837, by M. de Longchamps and 
